The vertical composition profile of active layer has a major effect on the performance of organic photovoltaic devices (OPVs). While stepwise deposition of different materials is a conceptually straightforward method for controlled preparation of multi-component active layers, it is practically challenging for solution processes because of dissolution of the lower layer. Herein, we overcome this difficulty by employing the photoprecursor approach, in which a soluble photoprecursor is solution-deposited then photoconverted in situ to a poorly soluble organic semiconductor. This approach enables solution-processing of the p-i-n triple-layer architecture that has been suggested to be effective in obtaining efficient OPVs. We show that, when 2,6-dithienylanthracene and a fullerene derivative PC71BM are used as donor and acceptor, respectively, the best p-i-n OPV affords a higher photovoltaic efficiency than the corresponding p-n device by 24% and bulk-heterojunction device by 67%. The photoprecursor approach is also applied to preparation of three-component p-i-n films containing another donor 2,6-bis(5&prime;-(2-ethylhexyl)-(2,2&prime;-bithiophen)-5-yl)anthracene in the i-layer to provide a nearly doubled efficiency as compared to the original two-component p-i-n system. These results indicate that the present approach can serve as an effective means for controlled preparation of well-performing multi-component active layers in OPVs and related organic electronic devices.

f7: (a) Comparison of J–V curves of devices F and I; solid lines: under AM1.5G illumination at 100 mW cm−2, dashed lines: in the dark. (b) Absorption spectra of DTA and EH-DBTA in the thin-film form: the lowest transition energies (Eg-abs) were determined at the intersection of the line tangent to the long wavelength side of the band and the corrected baseline. The thin films were prepared by spin-coating chloroform solutions (5 mg ml−1, 800 rpm, 30 s) of each compound atop glass substrates followed by photoirradiation (470 nm LED, 550 mW cm−2, 30 min). (c) The EQE, IQE, and UV–vis absorption spectra for device I.

Mentions:
The photovoltaic performances of the hetero p–i–n devices are summarized in Table 1 (runs 8–10) and their J–V curves are plotted in Figure S14. The highest PCE of 2.89% associated with a Voc of 0.91 V and a FF of 55.0% was obtained when the p-, i-, and n-layers were deposited from solutions of 5, 10, and 5 mg ml−1, respectively (device I). The PCE is nearly twice as high as that of the best homo p–i–n device (device F, PCE = 1.50%). Figure 7a compares the J–V curves of devices F and I, clearly showing that the improvement in JSC (from 3.78 to 5.78 mA cm−2) mostly accounts for the enhanced PCE.

f7: (a) Comparison of J–V curves of devices F and I; solid lines: under AM1.5G illumination at 100 mW cm−2, dashed lines: in the dark. (b) Absorption spectra of DTA and EH-DBTA in the thin-film form: the lowest transition energies (Eg-abs) were determined at the intersection of the line tangent to the long wavelength side of the band and the corrected baseline. The thin films were prepared by spin-coating chloroform solutions (5 mg ml−1, 800 rpm, 30 s) of each compound atop glass substrates followed by photoirradiation (470 nm LED, 550 mW cm−2, 30 min). (c) The EQE, IQE, and UV–vis absorption spectra for device I.

Mentions:
The photovoltaic performances of the hetero p–i–n devices are summarized in Table 1 (runs 8–10) and their J–V curves are plotted in Figure S14. The highest PCE of 2.89% associated with a Voc of 0.91 V and a FF of 55.0% was obtained when the p-, i-, and n-layers were deposited from solutions of 5, 10, and 5 mg ml−1, respectively (device I). The PCE is nearly twice as high as that of the best homo p–i–n device (device F, PCE = 1.50%). Figure 7a compares the J–V curves of devices F and I, clearly showing that the improvement in JSC (from 3.78 to 5.78 mA cm−2) mostly accounts for the enhanced PCE.

The vertical composition profile of active layer has a major effect on the performance of organic photovoltaic devices (OPVs). While stepwise deposition of different materials is a conceptually straightforward method for controlled preparation of multi-component active layers, it is practically challenging for solution processes because of dissolution of the lower layer. Herein, we overcome this difficulty by employing the photoprecursor approach, in which a soluble photoprecursor is solution-deposited then photoconverted in situ to a poorly soluble organic semiconductor. This approach enables solution-processing of the p-i-n triple-layer architecture that has been suggested to be effective in obtaining efficient OPVs. We show that, when 2,6-dithienylanthracene and a fullerene derivative PC71BM are used as donor and acceptor, respectively, the best p-i-n OPV affords a higher photovoltaic efficiency than the corresponding p-n device by 24% and bulk-heterojunction device by 67%. The photoprecursor approach is also applied to preparation of three-component p-i-n films containing another donor 2,6-bis(5&prime;-(2-ethylhexyl)-(2,2&prime;-bithiophen)-5-yl)anthracene in the i-layer to provide a nearly doubled efficiency as compared to the original two-component p-i-n system. These results indicate that the present approach can serve as an effective means for controlled preparation of well-performing multi-component active layers in OPVs and related organic electronic devices.